VCSELs inherently produce a high optical power output, and this output cana be significantly higher than the maximum limit for eye safety applicable to many fiber optic systems, such as Fiber channel and Ethernet applications.
As a result one of the problems that has been faced in the prior art is how to maintain adequate power when the VCSEL is coupled to an optical fiber while preventing the VCSEL from emitting dangerous radiation when not attached to a fiber.
Various techniques have been used to make such a diode safe. One technique involves the use of an electromechanical shutter to cut off optical power when the fiber is detached and shut the VCSEL off. Another technique requires the use of a calibrated monitor diode.